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AGNT40 KWNM 231330

.Marine Weather Discussion for N Atlantic Ocean
.NWS Ocean Prediction Center Washington DC
930 AM EDT FRI 23 JUN 2017

.FORECAST DISCUSSION...Major features/winds/seas/significant
.weather for the North Atlantic Ocean W of 50W from 30N to 50N.

The latest models are consistent that the south to southwest
winds across the offshore waters will gradually increase tonight
through Saturday evening. There is some potential for winds to
reach marginal gales across the northern outer NT2 waters over
the Gulf Stream Saturday afternoon and evening. With this
mornings forecast updates will continue to limit the winds to 30
kt, but will watch the trend in today`s 12Z guidance. At the
moment we do not have sufficient forecast confidence to upgrade
these outer zones to gales. The strength of the winds at the
surface will largely depend on how stable the lower levels
remain over the Gulf Stream. The 4km NAM which usually handles
this better than the GFS, is obly showing marginally unstable
low level lapse rates. The 00Z/06Z Wavewatch III and 00Z ECMWF
WAM are both well initialized with the west Atlantic wave
heights this morning. We will not be making any significant
adjustments to the previous OPC forecast grids.

...Previous Discussion...

Summary...The 00z ncep surface analysis shows a warm front
extending roughly se to nw across the nrn nt2 and srn nt1
waters, with high pres ridges over most of the nt1 waters and
across the srn and central nt2 waters. Latest available ascat
hi-res and ascat passes from a few hours ago indicate 5 to 15 kt
winds over the offshore waters.

Models...00z medium range models are in good overall agreement
across the offshore waters through the forecast period, although
there are some minor timing differences evident for Tue and Tue
Night. However, the 00z gfs 10m solution has good support from
the latest wpc medium range forecaster guidance and appears to
be representative enough to be used for the wind grids over the
entire forecast period.

Seas...The 00z wna wavewatch and 00z ecmwf wam both initialized
reasonably well over the coastal/offshore waters. The models are
in good overall agreement across the offshore waters over the
entire forecast period, with only minor differences noted. A
representative 50/50 blend of the 00z wna wavewatch/ecmwf wam
will be used for the sea height grids for the entire forecast
period, in order to smooth out the model differences.

.Extratropical Storm Surge Guidance...N/A.


.NT1 New England Waters...

.NT2 Mid-Atlantic Waters...


.Forecaster Clark/Scovil. Ocean Prediction Center. is the U.S. government's official web portal to all federal, state and local government web resources and services.